Tunneling spectra of NbSe3 in magnetic fields

The charge density wave gaps of NbSe3 have been carefully determinated by tunneling spectroscopy. In contrast to earlier work, the gap parameter associated with the 59 K transition obtained in the present measurements is very close to the mean field value. The gap structures for both the 145 K and 59 K transitions are found to be essentially independent of the applied magnetic field H. The present findings strongly suggest that the anomalous magnetotransport properties of the material originate from some other mechanism than a X-induced improvement of Fermi surface nesting.